An internal combustion (IC) engine in the form of a diesel engine has been used for commercial, industrial, agricultural and other heavy duty applications for well over 100 years. The fundamental diesel engine cycle promotes high part-power fuel efficiency and has therefore become the engine type of choice for commercial and agricultural purposes. Although the diesel engine has outstanding efficiency and long term durability, environmental issues have increased in significance with substantial increases in urban populations throughout the world. As a result, governmental regulations have become increasingly more stringent with respect to exhaust emissions from diesel engines. Nowhere is this more evident than in the United States, beginning with the Environmental Protection Agency (EPA) established over 30 years ago. During the ensuing years, the EPA has proposed and adopted ever increasing emissions limits for on-highway vehicles. The application of these standards has now been applied to off-road vehicles such as tractors, combines and other vehicles not normally driven on public highways including power generation systems. The EPA has adopted successive tiers of emissions requirements and the most recent is Tier IV. This requirement necessitates a diesel particulate filter (DPF) along with a requirement for regeneration of the filter to remove particulate matter accumulated on the filter.
A number of systems have been proposed to regenerate filters, relying on the fact that diesel particulate matter combusts when local temperatures are above 600° C. These systems may include engine management, resistive heating coils, microwave generation, and a fuel burner to increase the exhaust temperature. Another system is hydrocarbon injection in the form of atomized fuel directly into the exhaust upstream from a diesel oxidation catalyst (DOC) to increase the exhaust temperature around the filter. One of the problems with such a system is that the fuel nozzle and lines leading to the nozzle are subjected to high ambient temperatures reaching into the region where the hydrocarbon fuel tends to coke and form deposits in the fuel nozzle and associated supply passages.